Neuromolecular Etiology of Bipolar Disorder: Possible Therapeutic Targets of Mood Stabilizers

Bipolar disorder is a mental illness that causes extreme mood swings and has a chronic course. However, the mechanism by which mood episodes with completely opposite characteristics appear repeatedly, or a mixture of symptoms appears, in patients with bipolar disorder remains unknown. Therefore, mood stabilizers are indicated only for single mood episodes, such as manic episodes and depressive episodes, and no true mood-stabilizing drugs effective for treating both manic and depressive episodes currently exist. Therefore, in this review, therapeutic targets that facilitate the development of mood stabilizers were examined by reviewing the current understanding of the neuromolecular etiology of bipolar disorder.

N-acetyl-D-glucosamine kinase interacts with dynein light-chain roadblock type 1 at Golgi outposts in neuronal dendritic branch points

N-acetylglucosamine kinase (GlcNAc kinase or NAGK) is a ubiquitously expressed enzyme in mammalian cells. Recent studies have shown that NAGK has an essential structural, non-enzymatic role in the upregulation of dendritogenesis. In this study, we conducted yeast two-hybrid screening to search for NAGK-binding proteins and found a specific interaction between NAGK and dynein light-chain roadblock type 1 (DYNLRB1). Immunocytochemistry (ICC) on hippocampal neurons using antibodies against NAGK and DYNLRB1 or dynein heavy chain showed some colocalization, which was increased by treating the live cells with a crosslinker. A proximity ligation assay (PLA) of NAGK-dynein followed by tubulin ICC showed the localization of PLA signals on microtubule fibers at dendritic branch points. NAGK-dynein PLA combined with Golgi ICC showed the colocalization of PLA signals with somal Golgi facing the apical dendrite and with Golgi outposts in dendritic branch points and distensions. NAGK-Golgi PLA followed by tubulin or DYNLRB1 ICC showed that PLA signals colocalize with DYNLRB1 at dendritic branch points and at somal Golgi, indicating a tripartite interaction between NAGK, dynein and Golgi. Finally, the ectopic introduction of a small peptide derived from the C-terminal amino acids 74-96 of DYNLRB1 resulted in the stunting of hippocampal neuron dendrites in culture. Our data indicate that the NAGK-dynein-Golgi tripartite interaction at dendritic branch points functions to regulate dendritic growth and/or branching.

Neuronal activation increases the density of eukaryotic translation initiation factor 4E mRNA clusters in dendrites of cultured hippocampal neurons

Activity-dependent dendritic translation in CNS neurons is important for the synapse-specific provision of proteins that may be necessary for strengthening of synaptic connections. A major rate-limiting factor during protein synthesis is the availability of eukaryotic translation initiation factor 4E (eIF4E), an mRNA 5'-cap-binding protein. In this study we show by fluorescence in situ hybridization (FISH) that the mRNA for eIF4E is present in the dendrites of cultured rat hippocampal neurons. Under basal culture conditions, 58.7 +/- 11.6% of the eIF4E mRNA clusters localize with or immediately adjacent to PSD-95 clusters. Neuronal activation with KCl (60 mM, 10 min) very significantly increases the number of eIF4E mRNA clusters in dendrites by 50.1 and 74.5% at 2 and 6 h after treatment, respectively. In addition, the proportion of eIF4E mRNA clusters that localize with PSD-95 increases to 74.4 +/- 7.7% and 77.8 +/- 7.6% of the eIF4E clusters at 2 and 6 h after KCl treatment, respectively. Our results demonstrate the presence of eIF4E mRNA in dendrites and an activity-dependent increase of these clusters at synaptic sites. This provides a potential mechanism by which protein translation at synapses may be enhanced in response to synaptic stimulation.

Sorting Nexin 17 Interacts Directly with Kinesin Superfamily KIF1B beta Protein

KIF1B beta is a member of the Kinesin superfamily proteins (KIFs), which are microtubule-dependent molecular motors that are involved in various intracellular organellar transport processes. KIF1B beta is not restricted to neuronal systems, however, is widely expressed in other tissues, even though the function of KIF1B beta is still unclear. To elucidate the KIF1B beta-binding proteins in non-neuronal cells, we used the yeast two-hybrid system, and found a specific interaction of KIF1B beta and the sorting nexin (SNX) 17. The C-terminal region of SNX17 is required for the binding with KIF1B beta. SNX17 protein bound to the specific region of KIF1B beta (813-916. aa), but not to other kinesin family members. In addition, this specific interaction was also observed in the Glutathione S-transferase pull-down assay. An antibody to SNX17 specifically co-immunoprecipitated KIF1B beta associated with SNX17 from mouse brain extracts. These results suggest that SNX17 might be involved in the KIF1B beta-mediated transport as a KIF1B beta adaptor protein.

Kinesin Superfamily KIF1Balpha Protein Binds to the PDZ Domain of MALS-3 / 대한해부학회지

The Kinesin superfamily proteins (KIFs) make up a large superfamily of molecular motors that transport cargo such as vesicles, protein complexes, and organelles. KIF1Balpha is a monomeric motor that conveys mitochondria and plays an important role in cellular function. Here, we used the yeast two-hybrid system to identify the proteins that interacts with KIF1Balpha and found a specific interaction with the mammalian LIN-7 (MALS)-3/vertebrate homology of LIN-7 (Veri) and synaptic scaffolding molecule (S-SCAM). MALS-3 protein bound to the tail region of KIF1Balpha but not to other kinesin family members in the yeast two-hybrid assay. The "T-X-V" motif at the C-terminal end of KIF1Balpha is essential for interaction with MALS-3. In addition, this protein showed specific interactions in the Glutathione S-transferase (GST) pull-down assay. An antibody to MALS-3 specifically coimmunoprecipitated KIF1Balpha associated with MALS-3 from mouse brain extracts. These results suggest that MALS-3, as KIF1Balpha receptor, is involved in the KIF1Balpha-mediated transport.

Kinesin Superfamily KIF1A Protein Binds to Synaptotagmin XI / 대한해부학회지

The kinesin proteins (KIFs) make up a large superfamily of molecular motors that transport cargo such as vesicles, protein complexes, and organelles. KIF1A is a monomeric motor that conveys synaptic vesicle precursors and plays an important role in neuronal function. Here, we used the yeast two-hybrid system to identify the neuronal protein (s) that interacts with the tail region of KIF1A and found a specific interaction with synaptotagmin XI. The amino acid residues between 830 and 1300 of KIF1A are required for the interaction with synaptotagmin XI. KIF1A also bound to the tail region of synaptotagmin IV but not to other synaptotagmin in the yeast two-hybrid assay. KIF1A interacted with GST-synaptotagim XI fusion proteins, but not with GST alone. An antibody to synaptotagmin XI specifically co-mmunoprecipitated KIF1A associated with synaptotagimin from mouse brain extracts. These results suggest that KIF1A motor protein transports of synaptotagmin XI-containing synaptic vesicle precursors along microtubule.

Molecular Motor Proteins of the Kinesin Superfamily Proteins (KIFs): Structure, Cargo and Disease

Intracellular organelle transport is essential for morphogenesis and functioning of the cell. Kinesins and kinesin-related proteins make up a large superfamily of molecular motors that transport cargoes such as vesicles, organelles (e.g. mitochondria, peroxisomes, lysosomes), protein complexes (e.g. elements of the cytoskeleton, virus particles), and mRNAs in a microtubule- and ATP-dependent manner in neuronal and non-neuronal cells. Until now, more than 45 kinesin superfamily proteins (KIFs) have been identified in the mouse and human genomes. Elucidating the transport pathways mediated by kinesins, the identities of the cargoes moved, and the nature of the proteins that link kinesin motors to cargoes are areas of intense investigation. This review focuses on the structure, the binding partners of kinesins and kinesin-based human diseases.

Kinesin Superfamily KIF5 Proteins Bind to betaIII Spectrin

The kinesin proteins (KIFs) make up a large superfamily of molecular motors that transport cargo such as vesicles, protein complexes, and organelles. KIF5 is a heterotetrameric motor that conveys vesicles and plays an important role in neuronal function. Here, we used the yeast two-hybrid system to identify the neuronal protein (s) that interacts with the tail region of KIF5 and found a specific interaction with betaIII spectrin. The amino acid residues between 1394 and 1774 of betaIII spectrin were required for the interaction with KIF5C. betaIII spectrin also bound to the tail region of neuronal KIF5A and ubiquitous KIF5B but not to other kinesin family members in the yeast two-hybrid assay. In addition, these proteins showed specific interactions, confirmed by GST pull-down assay and co-immunoprecipitation. betaIII spectrin interacted with GST-KIF5 fusion proteins, but not with GST alone. An antibody to betaIII spectrin specifically co-immunoprecipitated KIF5s associated with betaIII spectrin from mouse brain extracts. These results suggest that KIF5 motor proteins transport vesicles or organelles that are coated with betaIII spectrin.

Cloning of a pore-forming subunit of ATP-sensitive potassium channel from Clonorchis sinensis

A complete cDNA sequence encoding a pore-forming subunit (Kir6.2) of ATP-senstive potassium channel in the adult worm, Clonorchis sinensis, termed CsKir6.2, was isolated from an adult cDNA library. The cDNA contained a single open-reading frame of 333 amino acids, which has a structural motif (a GFG-motif) of the putative pore-forming loop of the Kir6.2. Peculiarly, the CsKir6.2 shows a lack-sequence structure, which deleted 57 amino acids were deleted from its N-terminus. The predicted amino acid sequence revealed a highly conserved sequence as other known other Kir6.2 subunits. The mRNA was weekly expressed in the adult worm.

Definition of the peptide mimotope of cellular receptor for hepatitis C virus E2 protein using random peptide library

BACKGROUND: Hepatitis C virus(HCV), a family of Flaviviridae, has a host cell-derived envelope containing a positive-stranded RNA genome, and has been known as the maj or etiological agent for chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma. There remains a need to dissect a molecular mechanism of pathogenesis for the development of therapeutic and effective preventive measure for HCV. Identification of cellular receptor is of central importance not only to understand the viral pathogenesis, but also to exploit strategies for prevention of HCV. This study was aimed at identifying peptide mimotopes inhibiting the binding of E2 protein of HCV to MOLT-4 cell . METHODS: In this study, phage peptide library displaying a random peptides consisting of 7 or 12 random peptides was employed in order to pan against E2 protein. Free HCV particles were separated from the immune complex forms by immunoprecipitation using anti-human IgG antibody, and used for HCV-capture ELISA. To identify the peptides inhibiting E2-binding to MOLT-4 cells, E2 protein was subj ect to bind to MOLT-4 cells under the competition with phage peptides. RESULTS: Several phage peptides were selected for their specific binding to E2 protein, which showed the conserved sequence of SHFWRAP from 3 different peptide sequences. They were also able to recognize the HCV particles in the sera of HCV patient s captured by monoclonal antibody against E2 protein. Two of them, showing peptide sequence of HLGPWMSHWFQR and WAPPLERSSLFY respectively, were revealed to inhibit the binding of E2 protein to MOLT-4 cell efficiently in dose dependent mode. However, few membrane-associated receptor candidates were seen using Fasta3 programe for homology search with these peptides. CONCLUSION: Phage peptides containing HLGPWMSHWFQR and WAPPLERSSLFY respectively, showed the inhibition of E2-binding to MOLT-4 cells. However, they did not reveal any homologues to cellular receptors from GenBank database. In further study, cellular receptor could be identified through the screening of cDNA library from MOLT-4 or hepatocytes using antibodies against these peptide mimotopes.